Lead Frame Silver Layers for Light Extraction
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Solution Overview
Problem
Conventional light emitting devices have not achieved a satisfactory level of improvement in light extraction efficiency, which is essential for applications requiring even light distribution and high luminance.
Innovation Solution
A lead frame with a base material and two or more silver-containing layers, where the uppermost layer contains sulfur and the lower layer is composed substantially of silver, is used to enhance light extraction efficiency. This configuration improves reflectance and luminance without increasing glossiness, allowing for even light emission without the need for diffusing materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a silver plating layer is used to improve light extraction efficiency, then reflectance is improved, but glossiness increases causing uneven light distribution
Solution Approach 1:
The silver plating layer is divided into multiple sub-layers (first silver-containing layer, second silver-containing layer, third silver-containing layer) with different compositions and properties. Each layer serves a specific function: the first layer provides high reflectance, the second layer controls glossiness, and the third layer enhances adhesion. This segmentation allows optimization of light extraction efficiency while maintaining even light distribution.
Solution Approach 2:
Different regions of the plating structure have different properties. The first silver-containing layer has high silver content for reflectance, while the second layer has lower silver content and contains sulfur compounds to reduce glossiness. This local differentiation of material composition enables simultaneous achievement of high light extraction efficiency and even light distribution.
2Illumination intensity
If multiple silver-containing layers are stacked to improve light extraction efficiency, then reflectance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The invention changes the parameters of the silver-containing layers systematically. Each layer has controlled thickness (e.g., first layer: 0.5-2.0 μm, second layer: 0.1-0.5 μm, third layer: 0.05-0.2 μm) and composition (silver content, sulfur compound concentration). By precisely controlling these parameters during electroplating, the complex multi-layer structure can be manufactured with consistent performance and high light extraction efficiency.
3Shape
If sulfur is added to the silver-containing layer to reduce glossiness, then light distribution is improved, but light extraction efficiency may be compromised
Solution Approach 1:
The sulfur-containing second silver-containing layer is positioned between the high-reflectance first layer and the base material, rather than as the outermost layer. This segmentation allows the sulfur compounds to reduce glossiness and improve light distribution without significantly affecting the overall reflectance provided by the first silver-containing layer. The third silver-containing layer with high silver content is restored on the outer surface to maintain high light extraction efficiency.
Solution Approach 2:
The second silver-containing layer with sulfur compounds acts as an intermediary layer between the high-reflectance first layer and the base material. It mediates between the conflicting requirements of high reflectance and low glossiness, allowing light to be effectively reflected while distributing it evenly. The sulfur compounds in this intermediate layer reduce glossiness without completely compromising the light extraction efficiency provided by the outer silver-containing layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly enhances light extraction efficiency, achieving high luminous flux and even light distribution, suitable for various applications including outdoor advertising and general lighting, while maintaining cost-effectiveness and simplicity in manufacturing.
Implementation Method 1
Many packages whose surface is provided with silver (Ag), which has high reflectance of the light from a light emitting element
Data Source
AI summary
A lead frame includes a base material and two or more silver-containing layers. The base material is composed of a metal. The two or more silver-containing layers are stacked on the base material. The two or more silver-containing layers includes an uppermost silver-containing layer containing sulfur, and a lower silver-containing layer. The lower silver-containing layer contains no selenium or the lower silver-containing layer is composed substantially only of silver. A method for manufacturing a light emitting device includes: preparing a lead frame; preparing a package including the lead frame; and mounting a light emitting element on the package. The lead frame is prepared by: providing a base material; forming an underlying metal on the base material by plating to form an underlayer; and forming two or more silver-containing stacked layers on the underlayer, the two or more silver-containing stacked layers including an uppermost silver-containing layer containing sulfur.